default_value

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 562
        def default_value(value)
          # Boolean types
          return "t" if value =~ /true/i
          return "f" if value =~ /false/i

          # Char/String/Bytea type values
          return $1 if value =~ /^'(.*)'::(bpchar|text|character varying|bytea)$/

          # Numeric values
          return value if value =~ /^-?[0-9]+(\.[0-9]*)?/

          # Fixed dates / times
          return $1 if value =~ /^'(.+)'::(date|timestamp)/

          # Anything else is blank, some user type, or some function
          # and we can't know the value of that, so return nil.
          return nil
        end